A typical machine for conveying and cutting sheet material includes an endless conveyor belt forming a substantially flat, horizontal supporting surface for supporting a lay-up of sheet material to be cut. The supporting surface is porous and penetrable by a cutting knife to permit the knife to extend entirely through the lay-up in the vertical direction and cut pattern pieces, for example, from the lay-up. A vacuum is introduced into the supporting surface to create a vacuum bed, which firmly holds the lay-up against the supporting surface during a cutting operation.
The endless conveyor belt typically defines a horizontal and substantially flat upper run for supporting the lay-up of sheet material, a lower run located below the upper run, and two arcuate end sections, each extending between respective ends of the upper and lower runs. The conveyor belt often comprises a plurality of slat-like supports, which are pivotally coupled together on their ends forming an endless belt. In this type of machine, the adjacent supports forming the transition between the ends of the upper run and the arcuate end sections are pivoted relative to each other, thus forming a gap between each end of the upper run and the respective arcuate end section of the belt. Each gap exposes an elongated side face of the support located at the respective end of the upper run, which permits air to leak into the vacuum created between the lay-up of sheet material and the supporting surface of the conveyor. This leakage can be substantial, typically requiring the vacuum pumps to be oversized in order to compensate for the leakage and provide a sufficient vacuum to hold the lay-up firmly against the supporting surface of the conveyor.
In one prior art machine, flexible barrier strips made of latex, for example, are each attached to one elongated side face of each slat-like support, so that when the supports are located in the upper run of the conveyor, the barrier strips are sandwiched between supports to prevent the cross-flow of air from one support to the next. In order to adequately seal one support from the next, the barrier strips extend from the base of each support to the plane of the supporting surface. This places the barrier strips in the path of the cutting knife, however, which cuts the barrier strips, and ultimately destroys their ability to adequately seal one support from the next. Unless the barrier strips are frequently replaced, which is a time-consuming and relatively expensive procedure, the leakage through the strips, and thus through the end portions of the vacuum bed can be substantial.
It is an object-of the present invention to overcome the drawbacks and disadvantages of such prior art machines.